The present invention relates to a solenoid for a solenoid valve mounted to a solenoid valve for driving a channel-switching valve member.
A solenoid valve 50 previously proposed by the present applicant shown in FIG. 4 comprises a valve portion 51 provided therein with a channel-switching valve member (not shown) and a solenoid portion 52 connected to the valve portion 51 for driving the valve member, and the valve member of the valve portion 51 is pushed by a push rod 60 and opened and closed.
The solenoid portion 52 is structured such that a cylindrical magnetic case 53 is provided at its one end with an opening to which the valve portion 51 is connected, a bobbin 55 having a coil 54 wound around an outer periphery of the bobbin 55, a magnetic plate 59 mounted to an opened end of the magnetic case 53, a stationary core 56 and a moving core 58 inserted into the magnetic plate 59 and the center hole of the bobbin 55 are assembled in the magnetic case 53. The stationary core 56 includes a flange portion 56a, and a core 56b having a pole face 56c. The core 56b is inserted through center holes of the magnetic plate 59 and the bobbin 55. The moving core 58 is slidably inserted into the center hole, one end of the moving core 58 is opposed to the pole face 56c, a cap 61 is press-fitted into the other end projecting from the center hole, the cap 61 is abutted against the push rod 60, and a reference portion of the cap 61 is provided with an abutting portion 61a which moves toward and away from the magnetic plate 59.
The cap 61 is provided at its outer periphery with a flange 61b, a return spring 57 is compressed between the flange 61b and the magnetic plate 59, thereby always biasing the moving core 58 in an abutting direction against the push rod 60, i.e., toward the valve portion 51.
In the solenoid valve 50 having such a structure, if the coil 54 of the solenoid portion 52 is energized, the moving core 58 is adsorbed by the pole face 56c of the stationary core 56 as shown in right half of FIG. 4, an abutting portion 61a of the cap 61 abuts against the magnetic plate 59 and stops. On the other hand, in a non-energized state, the moving core 58 moves away from the pole face 56c by the biasing force of the return spring 57 toward the valve portion 51 as shown in left half of FIG. 4, thereby pushing the magnetic plate 59, and associatively, the valve member is driven.
The solenoid portion 52 has the stationary core 56 of complicated shape comprising the flange portion 56a and the core 56b, but the present inventors made sure that it was unnecessary to especially provide such a stationary core having the complicated shape, and that sufficient magnetic attraction force could be exhibited to drive the moving core by a simple structure in which other member functions as the stationary core. If the solenoid portion is produced by this method, the number of parts can be reduced, the assembling process is simplified, and the producing cost can be reduced.
Thereupon, it is an object of the present invention to provide a solenoid for a solenoid valve capable of reducing the number of parts to simplify the assembling process and to reduce the producing cost by allowing other member to function as a stationary core.
To solve the achieve the above object, the present invention provides a solenoid for a solenoid valve mounted to a solenoid valve for driving a channel-switching valve member, wherein the solenoid comprises a non-magnetic bobbin having a center hole extending in a axial direction of the bobbin and wound around an outer periphery; a magnetic case having a side wall portion covering a side surface of the bobbin and an end wall portion integrally or separately formed on or from the side wall portion for covering one end surface of the bobbin in the axial direction and having substantially uniform thickness; an annular magnetic plate having a center hole coaxially connected to the center hole of the bobbin and connected to the magnetic case on the side of another end surface of the bobbin; and a moving core movably accommodated in the bobbin and the center hole of the magnetic plate; and wherein the end wall portion of the magnetic case also functions as a stationary core, a portion of the end wall portion covering the center hole of the bobbin is provided with a pole face for adsorbing the moving core.
In the present invention, the side wall portion and the end wall portion of the magnetic case may be integrally formed together, and they may have uniform thickness as a whole.
Alternatively, the side wall portion and the end wall portion of the magnetic case may be separately formed from each other and a thickness of the end wall portion may be greater than that of the side wall portion.
Further, an inner surface of the end wall portion of the magnetic case covering one end surface of the bobbin in the axial direction may be flat as a whole, or a portion of the end wall portion of the magnetic case covering the center hole of the bobbin may be provided with a cylindrical recess which is fitted into the center hole.
According to the solenoid of the present invention having the above structure, since a portion of the magnetic case also functions as the stationary core, it is unnecessary to provide a stationary core having the complicated shape unlike the prior art and thus, it is possible to drive the moving core by a stationary core having a simple structure. As a result, when the solenoid portion is produced, it is possible to reduce the number of parts, to simplify the assembling process, and to reduce the producing cost.